The present invention relates to doors and in particular to apparatus for sealing doors to reduce the accoustic transmission thereof.
Throughout this specification, the term `door` is used to denote the structure inserted in an aperture in a wall to enable that aperture selectively to be opened or closed and includes, though not exclusively, windows, room dividers and moving walls in addition to room access doors.
It is a feature of all doors, that if they are to be relatively easy to open and close they must be clear of the top and bottom of their frame at least when they are moving. This applies equally to sliding, swinging and revolving doors. While the provision of a small gap at the bottom of the door makes for ease of operation it prevents the door acting as an efficient accoustic or gas-tight barrier. In some cases this can be overcome by providing a flange against which the door seats in the closed position. This is not suitable in most cases where the door extends to floor level since it would involve a stepped uneveness permanently present on the floor. It has also been proposed to mount a brush-like or spring-loaded member on the base of the closure member to prevent draughts. These devices must, however, be a compromise since they cannot provide such a powerful seal that the opening and closing of the door becomes difficult.
It is an object of the invention to provide a door which can be sealed positively to reduce the accoustic transmission thereof.